Small-cell synovial sarcoma

Keratins 7, 1 3, and 19 are seen in 45% to 50% of cases of small cell synovial sarcoma, but less than 10% of differential diagnostic alternatives. 

POORLY DIFFERENTIATED SMALL-CELL SYNOVIAL SARCOMA... 

Pitfalls in the diagnosis of WT versus other kidney tumors include primary renal EWS/PNET, small cell synovial sarcoma, leukemia/lymphoma, and metastatic alveolar RMS. 

Antibodies to these PEMs are directed to the apical membrane portions of secretory mammary cells surrounding milk fat globules (mol wt >250 kDa). They react with a variety of epithelial tumors, including mesotheliomas. Like keratin, these antibodies are also expressed on synovial sarcomas, epithelioid sarcomas, and chordomas. They are not as reactive with as wide a variety of tumors as antikeratins. For instance, they do not react with many endocrine tumors. However, they may recognize some renal-cell carcinomas and small-cell anaplastic carcinomas... 

CD56 NK-lymphomas, neuroendocrine tumors (small cell carcinoma and carcinoid), pheochromocytoma, neuroblastoma, paraganglioma, Merkel cell tumor Schwannoma, synovial sarcoma, embryonal and alveolarrhabdomyosarcoma, meningioma, melanoma, chordoma, epithelioid sarcoma NK-cells, T-cells, cerebellum and brain cortex, neuromuscular junctions, neuroendocrine tissue, neurons, osteoblasts... 

T-cell lymphoma, ALCL, AML, GIST, breast metaplastic carcinoma, ovarian sex cord stromal tumors, synovial sarcoma, Merkel cell carcinoma, endocrine and neuroendocrine tumors, desmoplastic small round cell tumor, melanoma, nephroblastoma, ependymoma, mesenchymal chondrosarcoma, extrarenal malignant rhabdoid tumor, rhabdomyosarcoma, meningeal... 

Clear cell sarcoma, adenoid cystic carcinoma, small cell lung carcinoma, Ewing sarcoma, synovial sarcoma, osteosarcoma, angiosarcoma, AML,... 

In addition to epithelial neoplasms, a number of sarcomas, CNS tumors, small round cell tumors, and a few germ cell tumors may be positive with EMA. These tumors include malignant nerve sheath tumors, synovial sarcoma, leiomyosarcoma, malignant fibrous histiocytoma, epithelioid sarcoma, and chordoma. With the exception of the last two tumors mentioned, EMA immunostaining is focal. 

Mesothelin is a 40-kD glycoprotein of unknown function that is strongly expressed in mesothelial cells, ovarian serous cells, and pancreatic-bile duct cells. Using monoclonal antibody 5B2, Ordonez found it to immu-nostain normal mesothelial cells, mesotheliomas, non-mucinous ovarian carcinomas, and occasionally other neoplasms. Ordonez concluded that mesothelin staining could be used to diagnose mesotheliomas, although it was expressed in 14 of 14 ovarian carcinomas, 12 of 14 pancreatic ductal adenocarcinomas, 7 of 12 desmoplastic small round cell tumors, and 9 of 9 synovial sarcomas. Therefore, this antibody should be interpreted carefully. 

Few mesenchymal tumors including desmoplastic small round cell tumor, leiomyosarcoma and monophasic synovial sarcoma. 

The same t(14 18)(q32 q21) translocation described in the follicular lymphomas has been also identified in 15-35% of diffuse large B-cell lymphomas, a part of which seems to be transformed from the follicular lymphoma after the accumulation of other genetic abnormalities, in these cases the presence of the t(14 18) translocation indicates a poor prognosis. The overexpression of bd-2 is also found in many other lymphoid, myeloid and solid neoplasms. It is important to mention that the expression or the overexpression of bd-2 is not equivalent to the presence of the t(14 18) translocation-specific follicular lymphoma as it is expressed in many normal cells and in different tumors. The bd-2 is normally expressed in breast epithelium and many non-neoplastic lymphocytes including the small lymphocytes of mantle and marginal zones as well as thymus and many T-cell populations. Furthermore, bd-2 is frequently expressed in many soft tissue tumors such as solitary fibrous tumor, synovial sarcoma and rhabdomyosarcoma in addition to breast carcinoma and many lymphoma types as CLL and marginal cell lymphoma. 

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